Carrier Recombination in Passivated Polycrystalline Perovskite Thin Films

Organic-inorganic halide perovskites (OHPs) are the rising stars of photovoltaic and optoelectronic research [1-3]. With power conversion efficiencies surging from 3.8% to 22.7% [4,5] in the last 8 years, OHP solar cells will begin to compete with silicon-based technology in the coming years. However, high defect densities within perovskite materials lead to the parasitic loss of charge carriers via non-radiative recombination (NRR), limiting the efficiencies of state-of-the-art devices. Passivation treatments can be employed to render these defects inert. Such treatments include the chemical doping of perovskite solutions before processing, and the atmospheric post-treatment of films after fabrication [6-9]. The aim of my PhD project is to contribute to a better understanding of the mechanisms that drive NRR in polycrystalline perovskite films, and to uncover the physics behind the passivation treatments which are employed to eliminate defects. Utilising a combination of fast spectroscopy techniques (time-resolved photoluminescence spectroscopy, transient absorption spectroscopy, time-resolved photoemission electron microscopy...) my goal is to characterise the behaviour of carriers under the influence of various passivation methods, to reveal pathways towards more optimal treatments and enhanced device performance. I intend to focus on understanding the role of surface defects - shown to be the most dominant limit on efficiency in OHP thin films [10,11] - using existing surface recombination velocity models [12], as well as through the construction of a comprehensive model of hole-trapping in triple-cation perovskite.

References:
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